Due to environmental and health concerns, among other things, there has been a movement toward reducing the amount of volatile organic compounds (VOCs) in paints, stains, and other coating compositions. However, many coatings that are marketed as “low-VOC” or even “zero-VOC” still emit high quantities of volatile emissions such as ammonia which is inorganic and not accounted for in the VOC total. Furthermore, the performance of the paint system may decrease due to the absence of VOCs in coatings, and paint manufacturers have been searching for ways to develop better performing coating compositions with low volatile emissions. The quest for a better “green paint” is discussed in a New York Times newspaper article entitled “The Promise of Green Paint” (Kershaw, Sarah, The New York Times, May 15, 2008, p. F6), which is incorporated herein by reference in its entirety.
Typically, additives that facilitate or impart desirable paint properties, such as better film coalescence from a latex, better resistance to blocking, better film durability, better physical and chemical scrub resistance, and tougher coatings, among others, contain volatile compounds, which evaporate into the environment upon film formation. The evaporation often results in undesirable aromas, and exposure to such fumes, particularly in areas that are not well ventilated, remains a health concern. Thus, less volatile or non-volatile compounds that impart comparable (or superior) properties to the paints are needed to replace higher VOC additives.
For instance, U.S. Pat. No. 6,762,230 B2 discloses paint compositions containing a latex polymer and dispersible coalescents having a VOC content less than about 50% wt. The '230 patent describes the dispersible coalescents as preferably having low molecular weight, though the examples indicate their structure as being formed by a reaction between ε-caprolactone and an alcohol or a carboxylic acid.
U.S. Pat. No. 6,069,200 discloses aqueous curable compositions comprising polymers with sterically hindered alkoxylated silane groups and acid groups blocked by fugitive bases. The '200 patent teaches that these groups can be crosslinked using organometallic catalysts. The compositions of the '200 patent are disclosed to be used as adhesives, sealants, and paints, and are disclosed to have improved properties including solvent resistance, adhesion, hardness, abrasion resistance, and mar resistance. The '200 patent, however, teaches the use of conventional VOC compositions.
U.S. Patent Application Publication No. 2004/0161542 A1 discloses an aqueous composition and method for preparing a non-yellowing coating therefrom. The '542 publication discloses compositions having less than 5 wt % VOCs and discloses that the compositions are useful for preparing crosslinked coatings. Although the '542 publication discloses low-VOC content, it does not demonstrably achieve low volatile emissions, and thus would still lead to odors.
However, the VOC information used in the paint industry does not account for volatile inorganic compounds and the amount of volatile compounds that actually evaporate during the painting process or when paints dry. Thus, there remains a need for an aqueous coating composition, with de minimis volatile emissions, that performs at least as well as conventional VOC paints.